Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating lease payment	$ 7.6	$ 8.2
Operating lease, expense	7.6	8.2
Operating lease right-of-use assets	26.1	$ 29.0
Operating lease, liability	$ 25.5
Operating lease, weighted average remaining lease term	15 years	14 years
Operating lease, weighted average discount rate	4.80%	4.60%
New Operating Leases
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 2.5	$ 1.6
Operating lease, liability	$ 2.5	$ 1.6
Non Cancellable Operating Leases
Lessee Lease Description [Line Items]
Operating lease, expense			$ 15.0
Leverkusen Facility Land Lease
Lessee Lease Description [Line Items]
Agreements expiry period	2050
Current Tio2 production capacity in Leverkusen facility	33.00%
Operating lease, liability	$ 7.6